MLB Advanced Media is developing and hosting the app. Their CEO recently did an interview with TechCrunch:http://techcrunch.com/2015/03/23/mlbs-bob-bowman-on-streaming-all-the-things/
They're also doing a lot more than just HBO and MLB:
3/18 Sonys PlayStation Vue
3/18 March Madness streaming for Turner
3/29 Wrestlemania
4/6 MLB Opening Day
4/12 HBO Now debut with Game Of Thrones
So I'd be a little patient with the app
They're also doing a lot more than just HBO and MLB:
3/18 Sonys PlayStation Vue
3/18 March Madness streaming for Turner
3/29 Wrestlemania
4/6 MLB Opening Day
4/12 HBO Now debut with Game Of Thrones
So I'd be a little patient with the app